The present invention relates to a position-adjustable steering column assembly, particularly for a motor vehicle.
More particularly, the invention relates to steering column assemblies with so-called electrical adjustment, that is to say, for example, by the agency of electric gear motor means, as opposed to steering column assemblies with so-called manual adjustment.
These steering column assemblies with so-called electrical adjustment allow a user to adjust the angular position and the axial position of a steering wheel, for example by acting on control members controlling the operation of the gear motors for moving the column assembly and therefore the steering wheel.
In the state of the art there is already known, for example from document EP-A-0,444,994 in the name of the Applicant Company, such a steering column assembly which includes a column support structure provided with two more-or-less vertical lateral flanges, and a steering shaft including two portions, one of which carries the steering wheel and the other of which is connected to the rest of the mechanism for steering the vehicle and which portions are mounted telescopically one in the other, so as to allow the adjustment of the axial position of the steering wheel, this shaft being mounted so that it can rotate in a column body capable of pivoting about a more-or-less horizontal axis between the two flanges of the support structure so as to allow the adjustment of the angular position of the steering wheel.
This body includes two portions which can be moved slidingly one in the other, one of which includes means for rotationally guiding and for axially blocking the shaft portion which carries the steering wheel and the other of which is articulated between the flanges of the support structure.
This assembly also includes means comprising an electric gear motor for adjusting the angular position of the steering wheel, and an electric gear motor for adjusting the axial position of the steering wheel, which are adapted so as to interact, on the one hand, with the support structure and, on the other hand, with the body portion associated with the shaft portion which carries the steering wheel, in order to allow the adjustment of the angular and axial positions of the steering wheel.
These electrical gear motors may be operated, for example, by the user, through the agency of control members arranged on the steering wheel or on the dashboard of the vehicle or through a control unit comprising means for memorizing these positions.
The axial movement of the body portion associated with the shaft portion which carries the steering wheel is provided, in the assembly described in this prior document, through the agency of a rack-pinion mechanism. The pinion is rotationally driven in one direction or the other by one of the electric gear motors in order to give rise to a linear movement of the rack, this rack also being connected to the corresponding body portion, so as to allow the adjustment of the axial position of the latter and therefore of the steering wheel.
The angular movement of this body portion, and therefore of the steering wheel, is provided by means of the other electric gear motor, also including an output pinion adapted to interact with a rack for moving means for suspending this column body portion, along inclined ramps of the lateral flanges of the support structure, so as to allow an adjustment of the angular position of this body, portion and therefore of the steering wheel.
However, this configuration, and in particular that of the means for adjusting the angular position of the steering wheel, are relatively complicated, because this angular position adjustment requires, on the one hand, the conversion of a rotational motion of the output shaft of the gear motor into a linear movement of the rack and, on the other hand, the conversion of the linear movement of the rack into an angular movement of the corresponding body portion.
There is also known, for example from document U.S. Pat. No. 4,691,587, another embodiment of a steering column assembly with so-called electric adjustment. In this assembly, the steering shaft is arranged in a column body fixed onto an intermediate support structure including means with a gear motor for adjusting the axial position of this body.
This intermediate support structure is mounted so that it can move angularly with respect to a support structure connected to the rest of the vehicle, by virtue of a operating lever which is articulated on the support structure and adapted to interact with movement means, the operation of which is controlled by other means with an adjustment gear motor, which other means are also articulated on the support structure.
However, it can be understood that this configuration is relatively complicated, bulky and has extremely high weight and cost price which are both very high.